1. Field of the Invention
The invention relates to a water treatment device, or more specifically relates to a water treatment device used for collection and removal of oil and suspended matter found in the treatment water, or for simple, reliable and efficient implementation of biological water treatment using microorganisms found in the treatment water, through forced generation of large currents in the form of circular currents, vertical vortices etc., and, in addition, small vortices in the form of turbulent flows, vortex lines, Hill's spherical vortices, vortex rings, Karman vortices, Taylor vortices etc., in the treatment water in the treatment tank.
The invention could be applied with effect to use as an equipment for water quality conservation at such facilities as rain water drainage pump stations, pump stations for combined sewers where rain water and sewage are drained through the same conduits, and at sewage treatment facilities.
2. Description of the Related Art
Water in rivers and lakes, as well as industrial and domestic wastewater, contains a large variety of impurities, including suspended matter such as oil and solids such as sand. The demand today for environmental conservation on a global scale calls for energy saving, centralization, efficiency and perfection in purification treatment of such water.
Methods used for purification treatment of water range from physical to chemical and biological treatment methods. In all cases, suspended matter such as oil and solids such as sand need to be removed as far as possible prior to purification treatment, as they are liable to directly or indirectly impair the purification treatment process.
Grit chambers and settling tanks have conventionally been used in removing sand and other solids in the treatment water, while screens and similar devices are normally used for the removal of suspended matter. The use, however, of settling tanks etc. is problematic in that such settling tanks etc. take up large sites and in that costly equipment with complex mechanisms are required for the removal of the sediments. When using screens for the removal of minute suspended solids, on the other hand, there arise problems such as the need for costly screens with fine meshes, and the problem of the blockage of the screens by the suspended solids.
As an improvement on the above-mentioned conventional technology, the Inventor has, in U.S. Pat. No. 5,246,583, proposed a low-cost and easy-to-handle solid-liquid separator, with which efficient solid-liquid separation is ensured by installing horizontally-rotating drums in vertical positions at approximate centers of settling tanks and treatment tanks for removal of oil and suspended matter at water treatment plants, and making use of the hydraulic characteristics of the flow generated in the treatment water by rotating the rotating drums.
With the solid-liquid separator, rapid and reliable separation of oil and solids from water is effected by rotating the rotating drums in the treatment water containing oil, solids etc. While, a significantly higher level of efficiency is, in fact, achieved in the separation of suspended matter such as oil and solids such as sand with the separator in comparison with conventional methods that do not utilize rotating drums, the level achieved in the separation of suspended matter may still not be adequate depending on the conditions at the installation positions. The separator has also been found wanting in its adaptability to water level fluctuation in treatment tanks.
Unlike chemical treatment methods which are liable to cause secondary pollution, biological wastewater treatment (water treatment) methods have been seeing wide application as an environment-friendly water treatment method. In the activated sludge process, for example, which is a typical biological treatment method, wastewater treatment is implemented in an aerobic environment by aerating the treatment water to raise the efficiency and speed of biological treatment. In the oxidation ditch method, instead of aeration, rotating drums are used to have the treatment water flow through a long water channel and have the treatment water absorb oxygen from the water surface while flowing through the channel. In other words, in these conventional methods, increasing the amount of oxygen entering the treatment water was seen as the only means of activating the microorganisms found in the wastewater, and with no other effective methods being found for activating microorganisms, there were limits to the extent to which one could hope to raise the efficiency of wastewater treatment.